In a Long Term Evolution (LTE) system, an evolved NodeB (eNodeB) is responsible for scheduling downlink data and uplink data of a user equipment (UE), and transmitting the downlink data and the uplink data over an air interface. However, for the uplink data of the user equipment, because the user equipment first generates the uplink data, the eNodeB needs to obtain uplink data information (for example, a size of a data volume) of the user equipment, so that the eNodeB can allocate, to the user equipment, a transmission resource suitable for sending the uplink data, so as to perform scheduling in time and accurately.
Specifically, as shown in FIG. 1, a procedure in which UE 1 requests a transmission resource for uplink data is as follows:
101: When UE 1 generates uplink data needing to be sent to UE 2, and UE 1 has no transmission resource for sending the uplink data, UE 1 sends a scheduling request (SR) to an eNodeB, to instruct the eNodeB to allocate, to UE 1, a transmission resource (1.5 ms) for sending the uplink data.
102: The eNodeB allocates an uplink grant (UL Grant) resource to UE 1, and sends the UL Grant to UE 1. The UL Grant is used by UE 1 to report data volume information of the uplink data buffered by UE 1 to the eNodeB (4 ms).
103: After UE 1 receives the UL grant allocated by the eNodeB, UE 1 sends a buffer status report (BSR) (4 ms) to the eNodeB on a transmission resource corresponding to the UL grant.
104: The eNodeB allocates, to UE 1 according to the received BSR, a transmission resource for sending the uplink data and a scheduling control resource, where the scheduling control resource is used to send a scheduling assignment (SA) when UE 1 sends the uplink data by using the allocated uplink data transmission resource; the eNodeB sends resource scheduling information to notify UE 1 of transmission resource information and scheduling control resource information (4 ms).
105: UE 1 sends the uplink data to UE 2 on the transmission resource, and sends an scheduling assignment to UE 2 on the scheduling control resource, where the scheduling assignment is used to notify UE 2 of information about a transmission format for sending the uplink data and transmission resource location information (4 ms) of the data.
Because UE 1 frequently communicates with UE 2, if the scheduling manner shown in FIG. 1 is still used, and UE 1 frequently communicates with the eNodeB, and excessively high overheads of transmission resources between the eNodeB and the user equipment are caused. Moreover, 17.5 ms is required for UE 1 to request an uplink data transmission resource by UE 1 from the eNodeB, the transmission delay is excessively long and cannot meet a low delay requirement (10 ms) of communication between UE 1 and UE 2.